Eye examinations are traditionally carried out in a well controlled environment, for example in an examination room in an optometrist's or ophthalmologist's office. In such environments the examiner can control lighting, distractions, and other influences that may compromise the accuracy of the examination. The examiner also has ample time to allow the examinee's eyes to adjust to changes in lighting.
Eye examinations are also carried out in less controlled environments. One example is a screening carried out on a large population of students in a school facility such as a gymnasium. The need to examine numerous students at a high tempo, and in relatively bright conditions is not inherently conducive to examination accuracy.
Another example is a retail outlet in a well lighted environment such as a shopping mall. If the outlet is not equipped with a controlled environment, the accuracy of the examination may suffer.
An additional difficulty arises if the examination requires the subject's eyes to be in a resting state of accommodation, which is a state in which there is no adequate stimulus for the subject's eyes to focus on. However in practice the subject may focus on the examiner or the examiner's equipment rather than maintain the desired resting state of accommodation. This difficulty can be especially prevalent when the subject is a child.
Therefore, there is a need to develop methods and equipment which enable an examiner to carry out an accurate vision examination in environments which are not well controlled and in which the subject may be unable or unwilling to maintain his eyes in a resting state of accommodation.